In a circuit, 3.3 V transistors under a 3.3 V environment are used. The circuit charges a universal serial bus (USB) when the USB is idle and has a voltage value of 0 V, for example. The USB, on the other hand, has a voltage value of 5 V in an operational mode. In addition, a special native NMOS transistor is designed to handle the 5 V of the USB in the 3.3 V environment. A native transistor is a transistor having a 0 V threshold voltage value.
As the size of transistors shrinks in line with the advent of process technology nodes, operational voltages for the transistors have decreased. In some applications, 3.3 V transistors are not suitable.
Like reference symbols in the various drawings indicate like elements.